What's this?

commandlinefu.com is the place to record those command-line gems that you return to again and again.
That way others can gain from your CLI wisdom and you from theirs too. All commands can be commented on, discussed and
voted up or down.

Check These Out

I have come across a situation in the past where someone has unlinked a file by running an 'rm' command against it while it was still being written to by a running process.
The problem manifested itself when a 'df' command showed a filesystem at 100%, but this did not match the total value of a 'du -sk *'.
When this happens, the process continues to write to the file but you can no longer see the file on the filesystem. Stopping and starting the process will, more often than not, get rid of the unlinked file, however this is not always possible on a live server.
When you are in this situation you can use the 'lsof' command above to get the PID of the process that owns the file (in the sample output this is 23521).
Run the following command to see a sym-link to the file (marked as deleted):
$ cd /proc/23521/fd && ls -l
Truncate the sym-link to regain your disk space:
$ > /proc/23521/fd/3
I should point out that this is pretty brutal and *could* potentially destabilise your system depending on what process the file belongs to that you are truncating.

If you don't want to delete them, but just want to list them, do
$ find -L /path -type l
If you want to delete them with confirmation first, do
$ find -L /path -type l -exec rm -i {} +
Using the -L flag follows symlinks, so the -type l test only returns true if the link can't be followed, or is a symlink to another broken symlink.

This command will show the current GMT time using HTTP. This might be useful if you just want to know what's the current human-readable and accurate-enough time, without changing the system time, using a simple command that would work regardless of the availability of NTP.
Note: To get a quicker and more accurate response, replace google.com with your local NTP server.
Also can be used as an alternative to the "htpdate" program:
http://www.commandlinefu.com/commands/view/668/set-your-computers-clock-using-http-and-htp-http-time-protocol-when-ntpsntp-is-not-available

Stay in the loop…

Follow the Tweets.

Every new command is wrapped in a tweet and posted
to Twitter. Following the stream is a great way of staying abreast of the latest commands. For the more discerning,
there are Twitter accounts for commands that get a minimum of 3 and 10 votes - that way only the great commands get tweeted.